The present invention pertains generally to polymeric materials and particularly to polymeric materials obtained from the reaction of phthalonitrile and epoxy compounds.
The use of structural adhesives and fiber-reinforced composites in aircraft, guided weapons, ships, and vehicle construction has increased markedly in the last decade and this dramatic growth rate shows every sign of continuing in the future. Conventional epoxy polymers are widely employed as the basis for adhesive compositions and as the matrix material for fiber-reinforced composites. These materials incorporate a latent curing agent and need only heat to initiate cure. When cured, epoxy polymers are highly crosslinked amorphous thermosetting polymers and this structure results in many useful properties such as high modulus, low creep, and good performance between 100.degree.-150.degree. C. Epoxies, however, have several disadvantages especially when being used as a matrix material for composites. Problems include complicated logistics of handling due to low temperature storage requirements for the prepreg with limited shelf life (commonly 6 months at--18.degree. C.), brittleness with poor resistance to crack growth, and engineering reliability attributed to delamination resulting from water penetration into the interface between the matrix material and the reinforcing fiber. In contrast, the prepregs of bisphenol-linked phthalonitrile polymers can be stored indefinitely until needed at room temperature without further reaction. The phthalonitrile polymers show excellent thermal stability when heated in air at 250.degree. C. for extended periods and are self-extinguishing on removal from a high temperature flame. These polymers also have a low affinity for water (&lt;1.2%), which makes them ideal candidates for composites and electronic applications. The phthalonitrile polymers, however, have the disadvantage of requiring higher cure temperatures and longer cure periods relative to the epoxies. In essence, an ideal high performance polymeric system would take advantage of the short cure times and low cure temperatures of the epoxies with the high temperature capability and water resistant of the bisphenol-linked polymers.
Several high performance bisphenol-linked polymers have been previously reported. These polymers can be cured neat or in the presence of organic amines, phenols, or metallic coreactants at 200.degree.-350.degree. C. to afford thermo-setting polymeric materials. Keller, U.S. Pat. No. 4,410,676 discloses a diether-linked phthalonitrile polymer which can withstand temperatures of 200.degree. C. for extended periods of time. U.S. Pat. No. 3,301,814 by Parry discloses a process for curing polyepoxies with phthalocyanines. The phthalocyanines form a "hem-like" structure which can complex metal ions. The complexed phthalocyanine then reacts with the epoxy functional group to form the desired polymer.
Prior disclosures, however, have not shown a process for producing a hydrophobic polymer which can operate at high temperatures and be produced with low cure temperatures and short cure times. A polymeric material is, therefore, needed which can combine the advantages of short cure times and low cure temperatures of the epoxies with the high temperature and water resistant advantages of the phthalonitriles.